How can you release the parking brake if you suspect the parking brake pump that is mounted on the torque converter has failed. Pressure is needed to release the parking brake because they are spring loaded in the rear hubs. Tranny speed sensor checks ok so does parking brake release valve. When scanner hooked up no trans rpm showing in any gear and no movement forward or reverse. Removed rear drive shaft then I get rpm and Tranny up shifts. This is why I believe even though parking brake shows to be released its not.
Adapt a manual hydraulic pump(with a gauge) to the park brake oil likes and pump them up to manufacturers pressure spec. What pressure is showing currently? Are the finals over full by any chance?
hope this helps but a serial number helps to give the correct information Mark
Final drive over full would be indication of what? Leaking piston seals from the brakes maybe? Also can that diverter valve cause this If the spool has moved going to check that.
Very likely. As suggested above adapt a portapower to pressurise the parking brake (right at the brakes themselves then you can test each one individually) and see if it holds pressure. If not there's your problem. While you're at it do the same test on the service brakes to see if the service brake piston seals are also leaking.
So I took line that goes tees of in the back and goes to the brakes and got no oil when brake release switch in cab put to release P brake. I took off the plug to get to the spool on parking brake control valve and found a broke spring. Then I removed spring and shims replaced plug now the brakes released when switched off from cab. Going to order spring now so if you have this issue inspect this spring in P brake valve on side of from frame.
Is this the valve you are referring to? I believe it is mounted on the inside of the right frame maybe a little back of the transmission? Been over a year since I saw the 769D at work!
Good that you have found the problem with the parking brake but you're still left the the fact that the rear axle housing is over-full with oil. I'd still suggest that you test both parking and service brake separately for each side to see if any brake piston seal is not holding pressure. So that would be 4 separate tests in total. If you find that all the brake piston seals are holding OK then there is still the possibility of brake cooling oil leaking into axle housing via the small Duo-Cone seal in one or both final drives. To test for this you have to blank off the brake cooling lines both into and out of one final drive at a time and pressurize to something like 30psi with a Portapower using 10W hydraulic oil. Once pumped up to the 30psi test pressure the gauge should not drop by more than about 10psi in 30 minutes IIRC. Some leakage in the Duo-Cone seals is acceptable.
Yes that is the valve.
What a beast of a truck !
Don't be saying that around Nige, the trucks he has dealt with make those little 769D's look like something for the grandkid to play in the sandbox with when he comes to visit! I spent a bit of time working on the various incarnations of the 769 Cats from the original 769(no letter) version up to the 769D's Also a few 773's up to the 773G that we got at work a couple years before I retired. But if you want a real Beast of a small truck go for a 1950's vintage Euclid with either a 6 cylinder Cummins or 6-71 Detroit running through a five speed manual transmission! Always felt the company should have held on to one of those at each quarry to keep around for the guys who complained about or abused the 769C-D trucks. A few hours in one of those would shut them up! Something along this line:
Believe it or not but the Product Line of which the 769 was part was affectionately referred to as "Lawns & Gardens" ......... Now either of the subjects of these two photos could be referred to as a beast of a truck ........
Lawn and garden! That's awesome!
That kind of hurts, I always tried telling people I worked on heavy equipment, now I just a Snapper lawn mower mechanic! Guess I deserve that as many of the motors I rebuilt were old two strokes, at least we did not have to mix oil in them. They did that on their own, what did not end up on the ground!
Well look at it this way, at least they never went rusty ......
Don't you Brits have a saying about "lubricating the undercart" ?
That's any Land Rover up to a Series 3. Oil leaks were always considered as standard equipment rather than an optional extra ........
Did they go by the same theory as the older Harleys? You knew they were low on oil if they didn't leave a puddle!
Probably ....... it's strange though that once a mechanic with a bit of "touch" has been round one for a while and put it together the way the designers originally intended generally the leaks seem to stop. Probably says more about 60s-70s-80s vehicle assembly standards than anything else.